Biosensor

ABSTRACT

A biosensor including light emitting elements and a light receiving element disposed on a principal surface of a wiring board; a light shielding portion disposed between a light-emitting-element sealing portion and a light-receiving-element sealing portion; a base medium having light transmitting properties, disposed in parallel with the wiring board with the light shielding portion therebetween; an adhesion layer having light transmitting properties that bonds the base medium with the light-emitting-element sealing portion, the light-receiving-element sealing portion, and the light shielding portion; and a first electrocardiograph electrode attached to a principal surface of the base medium. Both end portions of the adhesion layer and both end portions of the base medium are disposed such that they overlap neither of the light-receiving-element sealing portion nor the light-emitting-element sealing portion when viewed from a direction normal to the principal surface of the wiring board.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of PCT/JP2012/005065 filedAug. 9, 2012, which claims priority to Japanese Patent Application No.2011-179987, filed Aug. 19, 2011, the entire contents of each of whichare incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a biosensor which obtains biologicalsignals.

BACKGROUND OF THE INVENTION

These days, people are more and more concerned about health care andhealth maintenance and promotion. It is thus desirable that people canmore easily obtain biological information, such as the pulse andelectrocardiograms. Pulse monitors or pulse oximeters are known. Morespecifically, in such devices, by utilizing characteristics in whichhemoglobin within the blood absorbs light in a range from visible lightto infrared light, a change in the intensity of light passing through orreflected by a body, such as a finger, is obtained as aphotoplethysmographic signal.

Patent Document 1 discloses a biological information monitoring sensorwhich serves both as a body electrode and an oximeter probe. By usingthis biological information monitoring sensor, taking of anelectrocardiogram and measuring of oxygen saturation of hemoglobinwithin the blood can be performed simultaneously. More specifically,this biological information monitoring sensor includes an electrodeelement attached on a polymer film, an LED, which serves as a lightemitting element, and a PD, which serves as a light receiving element,fixed on the electrode element with a predetermined spacing between theLED and the PD, and AMPS, which serves as a transparent conductive gel,for covering the elements. With this configuration, when the sensorcontacts the skin surface of a body, the electrode element is broughtinto contact with the skin via the conductive AMPS, and thus, thefunction as a normal electrode element can be obtained. Meanwhile, theLED and the PD are in contact with the skin via the transparent AMPS,and thus, the function as an oximeter probe can be obtained.

Patent Document 1: Japanese Unexamined Utility Model RegistrationApplication Publication No. 6-29504

As stated above, in the biological information monitoring sensordisclosed in Patent Document 1, the light emitting element (LED) and thelight receiving element (PD) are covered with the transparent conductivegel (AMPS), and the LED and the PD contact a body skin via thetransparent AMPS. Accordingly, when monitoring is performed, part oflight emitted from the LED (detection light) may directly reach the PDvia the transparent AMPS. Normally, the intensity of light (stray light)emitted from the LED and reaching the PD without passing through orbeing reflected by a body is higher than the intensity of light passingthrough or being reflected by a body. Thus, light to be detected, thatis, light passing through or being reflected by a body, is embedded instray light (noise), which may decrease the S/N ratio.

SUMMARY OF THE INVENTION

The present invention has been made in order to solve theabove-described problem. It is an object of the present invention toprovide a biosensor which obtains photoplethysmographic signals andwhich is capable of reducing the amount of stray light which is receivedwithout passing through a body.

A biosensor according to the present invention includes: a wiring board;a light emitting element and a light receiving element disposed on aprincipal surface of the wiring board with a predetermined spacingbetween the light emitting element and the light receiving element; alight-emitting-element sealing portion having light transmittingproperties, disposed on the principal surface of the wiring board andconfigured to seal the light emitting element; a light-receiving-elementsealing portion having light transmitting properties, disposed on theprincipal surface of the wiring board and configured to seal the lightreceiving element; a light shielding portion disposed between thelight-emitting-element sealing portion and the light-receiving-elementsealing portion; a base medium having light transmitting properties,disposed in parallel with the wiring board with the light shieldingportion therebetween; an adhesion layer having light transmittingproperties, disposed between the base medium and the light shieldingportion and/or the light-emitting-element sealing portion and thelight-receiving-element sealing portion, and configured to bond the basemedium with the light shielding portion and/or thelight-emitting-element sealing portion and the light-receiving-elementsealing portion; and a plane electrode attached to a principal surfaceof the base medium such that the plane electrode overlaps neither of thelight emitting element nor the light receiving element when viewed froma direction normal to the principal surface of the wiring board, andconfigured to monitor a potential of a body. An end portion of theadhesion layer and an end portion of the base medium closer to the lightreceiving element are disposed such that the end portions do not overlapthe light-receiving-element sealing portion when viewed from thedirection normal to the principal surface of the wiring board.

In the biosensor according to the present invention, when a body, suchas a fingertip, contacts the front surface of the plane electrode, lightemitted from the light emitting element impinges on the body via thelight-emitting-element sealing portion, the adhesion layer, and the basemedium. Then, light passing through or reflected by the body is receivedby the light receiving element via the base medium, the adhesion layer,and the light-receiving-element sealing portion. With this operation, aphotoplethysmographic signal indicating a pulse wave of the body isobtained. Simultaneously, the potential of the body which is in contactwith the plane electrode is detected by the plane electrode.

In the biosensor according to the present invention, the light shieldingportion is disposed between the light-emitting-element sealing portionand the light-receiving-element sealing portion. Accordingly, lightemitted from the light emitting element is blocked from directlyimpinging on the light receiving element by the provision of the lightshielding portion. In the biosensor according to the present invention,the end portions of the base medium and the adhesion layer closer to thelight receiving element are disposed such that they do not overlap thelight-receiving-element sealing portion when viewed from the directionnormal to the principal surface of the wiring board. Accordingly, it isless likely that stray light propagating through the base medium and theadhesion layer and exiting from the end portions of the base medium andthe adhesion layer will impinge on the light-receiving-element sealingportion. It is thus possible to reduce the amount of stray light whichdoes not pass through a body and which is received after passing throughthe base medium and the adhesion layer. As a result, in the biosensorwhich obtains a photoplethysmographic signal, it is possible to reducethe amount of stray light which is received without passing through abody.

In the biosensor according to the present invention, an end portion ofthe adhesion layer and an end portion of the base medium closer to thelight emitting element may preferably be disposed such that the endportions do not overlap the light-emitting-element sealing portion whenviewed from the direction normal to the principal surface of the wiringboard.

With this configuration, it is less likely that light emitted from thelight emitting element will impinge on the end portions of the basemedium and the adhesion layer through the light-emitting-element sealingportion. It is thus possible to further reduce the amount of stray lightwhich does not pass through a body and which is transmitted through thebase medium and the adhesion layer.

A biosensor according to the present invention includes: a wiring board;a light emitting element and a light receiving element disposed on aprincipal surface of the wiring board with a predetermined spacingbetween the light emitting element and the light receiving element; alight-emitting-element sealing portion having light transmittingproperties, disposed on the principal surface of the wiring board andconfigured to seal the light emitting element; a light-receiving-elementsealing portion having light transmitting properties, disposed on theprincipal surface of the wiring board and configured to seal the lightreceiving element; a light shielding portion disposed between thelight-emitting-element sealing portion and the light-receiving-elementsealing portion; a base medium having light transmitting properties,disposed in parallel with the wiring board with the light shieldingportion therebetween; an adhesion layer having light transmittingproperties, disposed between the base medium and the light shieldingportion and/or the light-emitting-element sealing portion and thelight-receiving-element sealing portion, and configured to bond the basemedium with the light shielding portion and/or thelight-emitting-element sealing portion and the light-receiving-elementsealing portion; and a plane electrode attached to a principal surfaceof the base medium such that the plane electrode overlaps neither of thelight emitting element nor the light receiving element when viewed froma direction normal to the principal surface of the wiring board, andconfigured to monitor a potential of a body. An end portion of theadhesion layer and an end portion of the base medium closer to the lightemitting element are disposed such that the end portions do not overlapthe light-emitting-element sealing portion when viewed from thedirection normal to the principal surface of the wiring board.

In the biosensor according to the present invention, when a body, suchas a fingertip, contacts the front surface of the plane electrode, lightemitted from the light emitting element impinges on the body via thelight-emitting-element sealing portion, the adhesion layer, and the basemedium. Then, light passing through or reflected by the body is receivedby the light receiving element via the base medium, the adhesion layer,and the light-receiving-element sealing portion. With this operation, aphotoplethysmographic signal indicating a pulse wave of the body isobtained. Simultaneously, the potential of the body which is in contactwith the plane electrode is detected by the plane electrode.

In the biosensor according to the present invention, the light shieldingportion is disposed between the light-emitting-element sealing portionand the light-receiving-element sealing portion. Accordingly, lightemitted from the light emitting element is blocked from directlyimpinging on the light receiving element by the provision of the lightshielding portion. In the biosensor according to the present invention,the end portions of the base medium and the adhesion layer closer to thelight emitting element are disposed such that they do not overlap thelight-emitting-element sealing portion when viewed from the directionnormal to the principal surface of the wiring board. Accordingly, it isless likely that light emitted from the light emitting element willimpinge on the end portions of the base medium and the adhesion layerthrough the light-emitting-element sealing portion. It is thus possibleto further reduce the amount of stray light which does not pass througha body and which is transmitted through the base medium and the adhesionlayer. As a result, in the biosensor which obtains aphotoplethysmographic signal, it is possible to reduce the amount ofstray light which is received without passing through a body.

A biosensor according to the present invention includes: a wiring board;a light emitting element and a light receiving element disposed on aprincipal surface of the wiring board with a predetermined spacingbetween the light emitting element and the light receiving element; alight-emitting-element sealing portion having light transmittingproperties, disposed on the principal surface of the wiring board andconfigured to seal the light emitting element; a light-receiving-elementsealing portion having light transmitting properties, disposed on theprincipal surface of the wiring board and configured to seal the lightreceiving element; a light shielding portion disposed between thelight-emitting-element sealing portion and the light-receiving-elementsealing portion; and a cover having light transmitting properties,disposed in parallel with the wiring board with the light shieldingportion therebetween. An end portion of the cover closer to the lightreceiving element is disposed such that the end portion does not overlapthe light-receiving-element sealing portion when viewed from a directionnormal to the principal surface of the wiring board.

In the biosensor according to the present invention, when a body, suchas a fingertip, contacts the front surface of the cover, light emittedfrom the light emitting element impinges on the body via thelight-emitting-element sealing portion and the cover. Then, lightpassing through or reflected by the body is received by the lightreceiving element via the cover and the light-receiving-element sealingportion. With this operation, a photoplethysmographic signal indicatinga pulse wave of the body is obtained. In the biosensor according to thepresent invention, the light shielding portion is disposed between thelight-emitting-element sealing portion and the light-receiving-elementsealing portion. Accordingly, light emitted from the light emittingelement is blocked from directly impinging on the light receivingelement by the provision of the light shielding portion. In thebiosensor according to the present invention, the end portion of thecover closer to the light receiving element is disposed such that itdoes not overlap the light-receiving-element sealing portion when viewedfrom the direction normal to the principal surface of the wiring board.Accordingly, it is less likely that stray light propagating through thecover and reflected by the end portion of the cover will impinge on thelight-receiving-element sealing portion. It is thus possible to reducethe amount of stray light which does not pass through a body and whichis received after passing through the cover. As a result, in thebiosensor which obtains a photoplethysmographic signal, it is possibleto reduce the amount of stray light which is received without passingthrough a body.

In the biosensor according to the present invention, an end portion ofthe cover closer to the light emitting element may preferably bedisposed such that the end portion does not overlap thelight-emitting-element sealing portion when viewed from the directionnormal to the principal surface of the wiring board.

With this configuration, it is less likely that light emitted from thelight emitting element will impinge on the end portion of the coverthrough the light-emitting-element sealing portion. It is thus possibleto further reduce the amount of stray light which does not pass througha body and which is transmitted through the cover.

A biosensor according to the present invention includes: a wiring board;a light emitting element and a light receiving element disposed on aprincipal surface of the wiring board with a predetermined spacingbetween the light emitting element and the light receiving element; alight-emitting-element sealing portion having light transmittingproperties, disposed on the principal surface of the wiring board andconfigured to seal the light emitting element; a light-receiving-elementsealing portion having light transmitting properties, disposed on theprincipal surface of the wiring board and configured to seal the lightreceiving element; a light shielding portion disposed between thelight-emitting-element sealing portion and the light-receiving-elementsealing portion; and a cover having light transmitting properties,disposed in parallel with the wiring board with the light shieldingportion therebetween. An end portion of the cover closer to the lightemitting element is disposed such that the end portion does not overlapthe light-emitting-element sealing portion when viewed from a directionnormal to the principal surface of the wiring board.

In the biosensor according to the present invention, when a body, suchas a fingertip, contacts the front surface of the cover, light emittedfrom the light emitting element impinges on the body via thelight-emitting-element sealing portion and the cover. Then, lightpassing through or reflected by the body is received by the lightreceiving element via the cover and the light-receiving-element sealingportion. With this operation, a photoplethysmographic signal indicatinga pulse wave of the body is obtained. In the biosensor according to thepresent invention, the light shielding portion is disposed between thelight-emitting-element sealing portion and the light-receiving-elementsealing portion. Accordingly, light emitted from the light emittingelement is blocked from directly impinging on the light receivingelement by the provision of the light shielding portion. In thebiosensor according to the present invention, the end portion of thecover closer to the light emitting element is disposed such that it doesnot overlap the light-emitting-element sealing portion when viewed fromthe direction normal to the principal surface of the wiring board.Accordingly, it is less likely that light emitted from the lightemitting element will impinge on the end portion of the cover throughthe light-emitting-element sealing portion. It is thus possible tofurther reduce the amount of stray light which does not pass through abody and which is received after passing through the cover. As a result,in the biosensor which obtains a photoplethysmographic signal, it ispossible to reduce the amount of stray light which is received withoutpassing through a body.

In particular, in the biosensor according to the present invention, alateral surface of the end portion of the cover closer to the lightreceiving element may preferably be disposed such that the lateralsurface does not intersect with an imaginary line connecting a lightreceiving portion of the light receiving element and a peripheralportion of an opening of the light-receiving-element sealing portion.

With this configuration, it is even less likely that stray lightreflected by the end portion of the cover will impinge on thelight-receiving-element sealing portion. It is thus possible to moreeffectively reduce the amount of stray light which does not pass througha body and which is received after passing through the cover.

In the biosensor according to the present invention, a lateral surfaceof the end portion of the cover closer to the light emitting element maypreferably be disposed such that the lateral surface does not intersectwith an imaginary line connecting a light emitting portion of the lightemitting element and a peripheral portion of an opening of thelight-emitting-element sealing portion.

With this configuration, it is even less likely that light emitted fromthe light emitting element will impinge on the end portion of the coverthrough the light-emitting-element sealing portion. It is thus possibleto more effectively reduce the amount of stray light which does not passthrough a body and which is transmitted through the cover.

A biosensor according to the present invention includes: a wiring board;a light emitting element and a light receiving element disposed on aprincipal surface of the wiring board with a predetermined spacingbetween the light emitting element and the light receiving element; alight-emitting-element sealing portion having light transmittingproperties, disposed on the principal surface of the wiring board andconfigured to seal the light emitting element; a light-receiving-elementsealing portion having light transmitting properties, disposed on theprincipal surface of the wiring board and configured to seal the lightreceiving element; a light shielding portion disposed between thelight-emitting-element sealing portion and the light-receiving-elementsealing portion; a base medium having light transmitting properties,disposed in parallel with the wiring board with the light shieldingportion therebetween; and an adhesion layer having light transmittingproperties, disposed between the base medium and the light shieldingportion and/or the light-emitting-element sealing portion and thelight-receiving-element sealing portion, and configured to bond the basemedium with the light shielding portion and/or thelight-emitting-element sealing portion and the light-receiving-elementsealing portion. An end portion of the adhesion layer and an end portionof the base medium closer to the light receiving element are disposedsuch that the end portions do not overlap the light-receiving-elementsealing portion when viewed from a direction normal to the principalsurface of the wiring board.

In the biosensor according to the present invention, the light shieldingportion is disposed between the light-emitting-element sealing portionand the light-receiving-element sealing portion. Accordingly, lightemitted from the light emitting element is blocked from directlyimpinging on the light receiving element by the provision of the lightshielding portion. In the biosensor according to the present invention,the end portions of the base medium and the adhesion layer closer to thelight receiving element are disposed such that they do not overlap thelight-receiving-element sealing portion when viewed from the directionnormal to the principal surface of the wiring board. Accordingly, it isless likely that stray light propagating through the base medium and theadhesion layer and exiting from the end portions of the base medium andthe adhesion layer will impinge on the light-receiving-element sealingportion. It is thus possible to reduce the amount of stray light whichdoes not pass through a body and which is received after passing throughthe base medium and the adhesion layer. As a result, in the biosensorwhich obtains a photoplethysmographic signal, it is possible to reducethe amount of stray light which is received without passing through abody.

A biosensor according to the present invention includes: a wiring board;a light emitting element and a light receiving element disposed on aprincipal surface of the wiring board with a predetermined spacingbetween the light emitting element and the light receiving element; alight-emitting-element sealing portion having light transmittingproperties, disposed on the principal surface of the wiring board andconfigured to seal the light emitting element; a light-receiving-elementsealing portion having light transmitting properties, disposed on theprincipal surface of the wiring board and configured to seal the lightreceiving element; a light shielding portion disposed between thelight-emitting-element sealing portion and the light-receiving-elementsealing portion; a base medium having light transmitting properties,disposed in parallel with the wiring board with the light shieldingportion therebetween; and an adhesion layer having light transmittingproperties, disposed between the base medium and the light shieldingportion and/or the light-emitting-element sealing portion and thelight-receiving-element sealing portion, and configured to bond the basemedium with the light shielding portion and/or thelight-emitting-element sealing portion and the light-receiving-elementsealing portion. An end portion of the adhesion layer and an end portionof the base medium closer to the light emitting element are disposedsuch that the end portions do not overlap the light-emitting-elementsealing portion when viewed from a direction normal to the principalsurface of the wiring board.

In the biosensor according to the present invention, the light shieldingportion is disposed between the light-emitting-element sealing portionand the light-receiving-element sealing portion. Accordingly, lightemitted from the light emitting element is blocked from directlyimpinging on the light receiving element by the provision of the lightshielding portion. In the biosensor according to the present invention,the end portions of the base medium and the adhesion layer closer to thelight emitting element are disposed such that they do not overlap thelight-emitting-element sealing portion when viewed from the directionnormal to the principal surface of the wiring board. Accordingly, it isless likely that light emitted from the light emitting element willimpinge on the end portions of the base medium and the adhesion layerthrough the light-emitting-element sealing portion. It is thus possibleto further reduce the amount of stray light which does not pass througha body and which is transmitted through the base medium and the adhesionlayer. As a result, in the biosensor which obtains aphotoplethysmographic signal, it is possible to reduce the amount ofstray light which is received without passing through a body.

According to the present invention, in a biosensor which obtainsphotoplethysmographic signals, it is possible to reduce the amount ofstray light which is received without passing through a body.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a longitudinal sectional view of a biosensor according to afirst embodiment.

FIG. 2 is a plan view of a sensor unit forming the biosensor accordingto the first embodiment.

FIG. 3 shows plan views illustrating the configurations of sensor unitsof comparative examples.

FIG. 4 is a graph illustrating the relationship between the amount ofreceived stray light and the position of an end surface of a base mediumwith respect to a light receiving element.

FIG. 5 is a longitudinal sectional view of a biosensor according to asecond embodiment.

FIG. 6 is a longitudinal sectional view of a biosensor according to amodified example of the second embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of the present invention will be described belowwith reference to the drawings. In the drawings, the same elements aredesignated by like reference numerals, and an explanation of the sameelement will be given only once.

First Embodiment

The configuration of a biosensor 100 according to a first embodimentwill be described below with reference to FIGS. 1 through 3. FIG. 1 is alongitudinal sectional view of the biosensor 100. FIG. 2 is a plan viewof a sensor unit 110 forming the biosensor 100. In FIG. 1, a sectionalview taken along line I-I in FIG. 2 is shown.

The biosensor 100 is a sensor which performs simultaneous detection(monitoring) of items of biological information upon a fingertiptouching the biosensor 100, for example, taking of an electrocardiogramand measuring of the pulse and oxygen saturation are performed at thesame time. The biosensor 100 optically measures the pulse and oxygensaturation by utilizing absorption characteristics of hemoglobin withinthe blood, and at the same time, it electrically monitors a change inthe potential generated in accordance with the activity of the heart(takes an electrocardiogram) by using two electrodes 130 and 140.

The biosensor 100 includes two light emitting elements 121 and 122, alight receiving element 123, a first electrocardiograph electrode 130, asecond electrocardiograph electrode 140, base mediums 151 and 152, awiring board 160, a sealing section 170, and an adhesion layer 180.

The second electrocardiograph electrode 140 and the base medium 152 areintegrally formed. The base medium 152 is formed in a rectangular shape,and the second electrocardiograph electrode 140 is disposed on theprincipal surface of the base medium 152. The second electrocardiographelectrode 140 is formed in a rectangular shape such that the contour ofthe rectangle is smaller than that of the base medium 152. The basemedium 152 may be formed from a material, such as a resin. The basemedium 152 does not have to have light transmitting properties.

The two light emitting elements 121 and 122, the light receiving element123, the first electrocardiograph electrode 130, the base medium 151,the wiring board 160, the sealing section 170, and the adhesion layer180 are integrally formed. Hereinafter, for the sake of convenience,this integrally formed unit will be referred to as the “sensor unit110”. This sensor unit 110 is formed generally in a rectangularparallelepiped. In FIG. 1, the height is shown in a relatively enlargeddimension for representation.

The light emitting elements 121 and 122 and the light receiving element123 are mounted on a principal surface 160 a of the wiring board 160formed in a rectangular shape. The light emitting elements 121 and 122are disposed side by side on a shorter side of the wiring board 160 atone end portion of the principal surface 160 a. Meanwhile, the lightreceiving element 123 is disposed at the other end portion of theprincipal surface 160 a. The distance from the light emitting elements121 and 122 to the light receiving element 123 is set to be, forexample, about 4 to 20 mm.

The two light emitting elements 121 and 122 emit light beams ofdifferent wavelengths in order to obtain the ratio of oxyhemoglobin todeoxyhemoglobin indicating oxygen saturation within the blood. Forexample, the light emitting element 121 emits light around an infraredlight range in which the absorption coefficient of oxyhemoglobin ishigh. The light emitting element 122 emits light around a red lightrange in which the absorption coefficient of deoxyhemoglobin is high.

As the light emitting elements 121 and 122, LED, VCSEL, a resonator LED,or the like, may be used. As the light receiving element 123, aphotodiode, a phototransistor, or the like, may be suitably used.

The sealing section 170 is formed in the shape of a rectangularparallelepiped on the principal surface 160 a of the wiring board 160.The sealing section 170 includes a light-emitting-element sealingportion 171 for sealing the light emitting elements 121 and 122, alight-receiving-element sealing portion 172 for sealing the lightreceiving element 123, and a light shielding portion 173.

The light-emitting-element sealing portion 171 is formed from atranslucent resin in a columnar shape of a generally elliptical arc incross section and seals the light emitting elements 121 and 122. Thelight-emitting-element sealing portion 171 is exposed to a lateralsurface 170 a of the sealing section 170 on the side closer to the lightemitting elements 121 and 122. The light-receiving-element sealingportion 172 is formed from a translucent resin in a columnar shape of agenerally elliptical arc in cross section and seals the light receivingelement 123. The light-receiving-element sealing portion 172 is exposedto a lateral surface 170 b of the sealing section 170 on the side closerto the light receiving element 123. As the translucent resin forming thelight-emitting-element sealing portion 171 and thelight-receiving-element sealing portion 172, a transparent epoxy resin,for example, is used.

The light shielding portion 173 is formed by filling a resin havinglight-shielding properties into a region between thelight-emitting-element sealing portion 171 and thelight-receiving-element sealing portion 172 and into a peripheral regionoutside the light-emitting-element sealing portion 171 and thelight-receiving-element sealing portion 172 on the principal surface 160a of the wiring board 160. As the light shielding portion 173, forexample, an epoxy resin containing powder having light shieldingproperties, such as carbon black, is suitably used.

The top surfaces of the light-emitting-element sealing portion 171, thelight-receiving-element sealing portion 172, and the light shieldingportion 173 define a top surface 170 e of the sealing section 170. Thebase medium 151 formed in a rectangular shape is bonded to the topsurface 170 e of the sealing section 170 with the adhesion layer 180therebetween. A back surface 151 b of the base medium 151 is bonded tothe top surface 170 e of the sealing section 170 in a state in which itopposes the principal surface 160 a of the wiring board 160. The basemedium 151 and the adhesion layer 180 are formed in the same shape andare disposed such that they overlap each other.

An end portion 184 of the adhesion layer 180 and an end portion 154 ofthe base medium 151 closer to the light emitting elements 121 and 122are positioned such that they do not overlap an opening 171 a of thelight-emitting-element sealing portion 171 when viewed from a direction10 normal to the principal surface 160 a of the wiring board 160.

An end portion 185 of the adhesion layer 180 and an end portion 155 ofthe base medium 151 closer to the light receiving element 123 arepositioned such that they do not overlap an opening 172 a of thelight-receiving-element sealing portion 172 when viewed from thedirection 10 normal to the principal surface 160 a.

The adhesion layer 180 may be formed from, for example, an acrylicresin. If the adhesion layer 180 overlaps neither of the opening 171 aof the light-emitting-element sealing portion 171 nor the opening 172 aof the light-receiving-element sealing portion 172, the base medium 151and the adhesion layer 180 do not have to have light transmittingproperties.

The first electrocardiograph electrode 130 is formed in the shape of arectangular thin film and is disposed on a principal surface 151 a ofthe base medium 151. The first electrocardiograph electrode 130 isdisposed between the light emitting elements 121 and 122 and the lightreceiving element 123 when viewed from the direction 10 normal to theprincipal surface 160 a of the wiring board 160. Moreover, theelectrocardiograph electrode 130 is disposed at a position at which itoverlaps neither of the light emitting elements 121 and 122 nor thelight receiving element 123 and at a position at which it overlapsneither of the opening 171 a nor the opening 172 a when viewed from thedirection 10 normal to the principal surface 160 a.

A description will now be given, with reference to FIGS. 3 and 4, of therelationship between the amount of received stray light and thepositions of the end portions 155 and 185 of the base medium 151 and theadhesion layer 180, respectively, with respect to the light receivingelement 123 and the opening 172 a. Parts (a) through (d) of FIG. 3 areplan views illustrating the configurations of sensor units 111 through114 according to comparative examples. FIG. 4 is a graph illustratingthe relationship between the amount of received stray light and thepositions of the end portions 155 and 185 with respect to the positionof the light receiving element 123.

In the sensor units 111 through 114, the end portion 154 of the basemedium 151 and the end portion 184 of the adhesion layer 180 overlapeach other. In the sensor units 111 through 114, the end portions 154and 184 closer to the light emitting elements 121 and 122 are positionedsuch that they extend until the lateral surface 170 a of the sealingportion 170.

In the sensor units 111 through 114, the end portion 155 of the basemedium 151 and the end portion 185 of the adhesion layer 180 overlapeach other. In the sensor units 111 through 114, the positions of theend portions 155 and 185 with respect to the light receiving element 123and the opening 172 a of one sensor are different from those of anothersensor.

In the sensor unit 111, the positions of the end portions 155 and 185coincide with the position of the lateral surface 170 b of the sealingsection 170. The end portions 155 and 185 of the sensor unit 111 aredisposed such that a position X in a direction 11 with respect to thecenter of the light receiving element 123 is +2 mm from the end portions155 and 185. The direction 11 is a direction in which the light emittingelements 121 and 122 are connected to the light receiving element 123.In FIG. 3, the direction from the center of the light receiving element123 to the lateral surface 170 b (right side in FIG. 3) is a positivedirection.

In the sensor unit 112, the end portions 155 and 185 are positionedabove the center of the light receiving element 123, and are disposedsuch that the position X is 0 mm. In the sensor unit 113, the endportions 155 and 185 are positioned toward the left side of FIG. 3 fromthe center of the light receiving element 123 and are disposed such thatthe position X is −1 mm. In the sensor unit 114, the end portions 155and 185 are positioned toward the left side of FIG. 3 from the center ofthe light receiving element 123 and are disposed such that the positionX is −2 mm.

FIG. 4 illustrates the relationship between the amount of received straylight and the positions of the end portions 155 and 185 with respect tothe position of the light receiving element 123. In the graph of FIG. 4,the horizontal axis represents the position X (mm). The vertical axisrepresents the relative amount of stray light (%), which indicates therelative amounts of stray light of the above-described individual sensorunits 111 through 114 when the amount of stray light of the sensor unit112 (X=0 mm) is 100. The graph of FIG. 4 shows that, as the absolutevalue of the position X, that is, the distance from the light receivingelement 123 to the end portions 155 and 185, is increased, the relativeamount of stray light is decreased. Although the above-describeddistance of the sensor unit 111 is the same as that of the sensor unit114, the relative amount of stray light of the sensor unit 114 issmaller than that of the sensor unit 111.

The reason for this is as follows. In the sensor unit 114, the endportions 155 and 185 of the base medium 151 and the adhesion layer 180,respectively, are disposed at positions at which they do not overlap theopening 172 a of the light-receiving-element sealing portion 172.Accordingly, it is less likely that stray light which has propagatedthrough the base medium 151 and the adhesion layer 180 and which hasreached the end portions 155 and 185 will impinge on thelight-receiving-element sealing portion 172.

In the biosensor 100 according to this embodiment, when a fingertipcontacts the front surface of the first electrocardiograph electrode130, light emitted from the light emitting elements 121 and 122 impingeson the fingertip via the light-emitting-element sealing portion 171.Then, light passing through the fingertip is received by the lightreceiving element 123 via the light-receiving-element sealing portion172. With this operation, a photoplethysmographic signal indicating apulse wave of the fingertip is obtained. Simultaneously, the potentialof the fingertip which is in contact with the first electrocardiographelectrode 130 and the potential of a fingertip which is in contact withthe second electrocardiograph electrode 140 are detected.

In the biosensor 100 according to this embodiment, the end portions 155and 185 of the base medium 151 and the adhesion layer 180, respectively,closer to the light receiving element 123 are disposed such that they donot overlap the light-receiving-element sealing portion 172 when viewedfrom the direction 10 normal to the principal surface 160 a of thewiring board 160. Accordingly, it is less likely that stray lightpropagating through the base medium 151 and the adhesion layer 180 andexiting from the end portions 155 and 185 of the base medium 151 and theadhesion layer 180, respectively, will impinge on thelight-receiving-element sealing portion 172. It is thus possible toreduce the amount of stray light which does not pass through a body andwhich is received after passing through the base medium 151 and theadhesion layer 180.

Additionally, in the biosensor 100 according to this embodiment, the endportions 154 and 184 of the base medium 151 and the adhesion layer 180,respectively, closer to the light emitting elements 121 and 122 aredisposed such that they do not overlap the light-emitting-elementsealing portion 171 when viewed from the direction 10 normal to theprincipal surface 160 a of the wiring board 160. Accordingly, it is lesslikely that light emitted from the light emitting elements 121 and 122will impinge on the end portions 154 and 184 of the base medium 151 andthe adhesion layer 180, respectively, through the light-emitting-elementsealing portion 171. It is thus possible to further reduce the amount ofstray light which does not pass through a body and which is transmittedthrough the base medium 151 and the adhesion layer 180.

As a result, in the biosensor 100 of this embodiment whichsimultaneously obtains a photoplethysmographic signal and potentials ofa body (electrocardiogram), it is possible to reduce the amount of straylight which is received without passing through a body.

In this embodiment, photoelectric pulse waves and an electrocardiogramare obtained simultaneously. However, if an electrocardiogram is notobtained, that is, only photoelectric pulse waves are measured, theprovision of the first and second electrocardiograph electrodes 130 and140 is not necessary, and thus, the first and second electrocardiographelectrodes 130 and 140 may be omitted.

Second Embodiment

The configuration of a biosensor 200 according to a second embodimentwill be described below with reference to FIG. 5. FIG. 5 is alongitudinal sectional view of the biosensor 200.

The biosensor 200 is a sensor which performs detection (monitoring) ofbiological information, for example, measuring of the pulse and oxygensaturation, upon a fingertip touching the biosensor 200. The biosensor200 optically measures the pulse and oxygen saturation by utilizingabsorption characteristics of hemoglobin within the blood.

In order to implement this function, the biosensor 200 includes twolight emitting elements 221 and 222, a light receiving element 223, awiring board 260, a sealing section 270, and a cover 290.

The wiring board 260 is formed in a rectangular sheet-like shape. On thewiring board 260, the light emitting elements 221 and 222, the lightreceiving element 223, the sealing section 270, and the cover 290 areintegrally formed. Hereinafter, for the sake of convenience, thisintegrally formed unit will be referred to as the “sensor unit 210”.This sensor unit 210 is formed generally in a rectangularparallelepiped. In FIG. 5, the height is shown in a relatively enlargeddimension for representation. The sensor unit 210 is attached to acasing 900 which is made from an opaque resin by means of, for example,the insertion of the sensor unit 210 into a rectangular hole formed inthe casing 900. Alternatively, by using, for example, a sheet-likefixing member, the sensor unit 210 may be fixed by holding the sensorunit 210 from the rear surface of the wiring board 260.

The light emitting elements 221 and 222 and the light receiving element223 are mounted on a principal surface 260 a of the wiring board 260formed in a rectangular shape. The light emitting elements 221 and 222are disposed side by side on a shorter side of the wiring board 260 atone end portion of the principal surface 260 a. Meanwhile, the lightreceiving element 223 is disposed at the other end portion of theprincipal surface 260 a. The distance from the light emitting elements221 and 222 to the light receiving element 223 is set to be, forexample, about 4 to 20 mm.

The two light emitting elements 221 and 222 emit light beams ofdifferent wavelengths in order to obtain the ratio of oxyhemoglobin todeoxyhemoglobin indicating oxygen saturation within the blood. Forexample, the light emitting element 221 emits light around an infraredlight range in which the absorption coefficient of oxyhemoglobin ishigh. The light emitting element 222 emits light around a red lightrange in which the absorption coefficient of deoxyhemoglobin is high.

As the light emitting elements 221 and 222, LED, VCSEL (Vertical CavitySurface Emitting LASER), a resonator LED, or the like, may be used. Asthe light receiving element 223, a photodiode, a phototransistor, or thelike, may be suitably used.

The sealing section 270 is formed in the shape of a rectangularparallelepiped on the principal surface 260 a of the wiring board 260.The sealing section 270 includes a light-emitting-element sealingportion 271 for sealing the light emitting elements 221 and 222, alight-receiving-element sealing portion 272 for sealing the lightreceiving element 223, and a light shielding portion 273.

The light-emitting-element sealing portion 271 is formed from atranslucent resin in a cylindrical shape and seals the light emittingelements 221 and 222. The light-receiving-element sealing portion 272 isformed from a translucent resin in a cylindrical shape and seals thelight receiving element 223. As the translucent resin forming thelight-emitting-element sealing portion 271 and thelight-receiving-element sealing portion 272, a transparent epoxy resin,for example, is used.

The light shielding portion 273 is formed by filling a resin havinglight-shielding properties into a region between thelight-emitting-element sealing portion 271 and thelight-receiving-element sealing portion 272 and into a region around thelight-emitting-element sealing portion 271 and thelight-receiving-element sealing portion 272 on the principal surface 260a of the wiring board 260. The light shielding portion 273 defines fourlateral surfaces of the sealing section 270. As the light shieldingportion 273, for example, an epoxy resin containing powder having lightshielding properties, such as carbon black, is suitably used.

The top surfaces of the above-described light-emitting-element sealingportion 271, light-receiving-element sealing portion 272, and lightshielding portion 273 define a top surface 270 e of the sealing section270. The cover 290 having light transmitting properties is attached tothe top surface 270 e of the sealing section 270. That is, the cover 290is disposed in parallel with the wiring board 260 via the sealingsection 270 (light shielding portion 273). The cover 290 is a sheet-likemember having a thickness of about 0.1 to 2 mm made from an acrylic,polycarbonate, or PET (polyethylene terephthalate) resin havingtranslucent properties. The cover 290 is formed longer in thelongitudinal direction and in the widthwise direction than the sealingsection 270, and covers an opening 271 a of the light-emitting-elementsealing portion 271 and an opening 272 a of the light-receiving-elementsealing portion 272.

An end portion 294 of the cover 290 closer to the light emittingelements 221 and 222 is positioned farther outward than the opening 271a of the light-emitting-element sealing portion 271. That is, the endportion 294 of the cover 290 is disposed such that it does not overlapthe opening 271 a when viewed from the direction 10 normal to theprincipal surface 260 a of the wiring board 260. More specifically, thecover 290 is disposed such that the lateral surface (end surface) of theend portion 294 of the cover 290 closer to the light emitting elements221 and 222 does not intersect with an imaginary line 18 connecting thelight emitting portion (or the light emitting surface) of each of thelight emitting elements 221 and 222 and the peripheral portion of theopening 271 a of the light-emitting-element sealing portion 271.

An end portion 295 of the cover 290 closer to the light receivingelement 223 is positioned farther outward than the opening 272 a of thelight-receiving-element sealing portion 272. That is, the end portion295 of the cover 290 is disposed such that it does not overlap theopening 272 a when viewed from the direction 10 normal to the principalsurface 260 a. More specifically, the cover 290 is disposed such thatthe lateral surface (end surface) of the end portion 295 of the cover290 closer to the light receiving element 223 does not intersect with animaginary line 19 connecting the light receiving portion (or the lightreceiving surface) of the light receiving element 223 and the peripheralportion of the opening 272 a of the light-receiving-element sealingportion 272.

The detection of biological information by using the biosensor 200 isperformed by allowing a part of a body, for example, a fingertip of aleft hand of a patient, to contact the biosensor 200.

When detecting biological information, light emitted from the lightemitting elements 221 and 222 passes through the light-emitting-elementsealing portion 271 and impinges on the cover 290 through the opening271 a. Light then passes through the cover 290 and impinges on thefingertip.

Light incident on and passing through the fingertip further passesthrough the cover 290 and impinges on the opening 272 a of thelight-receiving-element sealing portion 272. Then, light passes throughthe light-receiving-element sealing portion 272 and is received by thelight receiving element 223. With this operation, a change in theintensity of light passing through the fingertip is obtained as aphotoplethysmographic signal. In this case, since light beams ofdifferent wavelengths are emitted from the two light emitting elements221 and 222, the intensity of the transmitted light concerning the twowavelengths can be obtained.

As discussed above in detail, according to this embodiment, when afingertip contacts the front surface of the biosensor 200, light emittedfrom the light emitting elements 221 and 222 impinges on the fingertipvia the light-emitting-element sealing portion 271 and the cover 290.Then, light passing through the fingertip is received by the lightreceiving element 223 via the cover 290 and the light-receiving-elementsealing portion 272. With this operation, a photoplethysmographic signalindicating a pulse wave of the fingertip is obtained.

In the biosensor 200, the light shielding portion 273 is disposedbetween the light-emitting-element sealing portion 271 and thelight-receiving-element sealing portion 272. Accordingly, light emittedfrom the light emitting elements 221 and 222 is blocked from directlyimpinging on the light receiving element 223 by the provision of thelight shielding portion 273. Moreover, in the biosensor 200, the endportion 295 of the cover 290 closer to the light receiving element 223is disposed such that it does not overlap the light-receiving-elementsealing portion 272 when viewed from the direction normal to theprincipal surface 260 a of the wiring board 260. Accordingly, it is lesslikely that stray light propagating through the cover 290 and reflectedby the end portion 295 of the cover 290 will impinge on thelight-receiving-element sealing portion 272. It is thus possible toreduce the amount of stray light which does not pass through a body andwhich is received through the cover 290. As a result, in the biosensor200 which obtains a photoplethysmographic signal, it is possible toreduce the amount of stray light which is received without passingthrough a body.

In particular, in the biosensor 200, the cover 290 is disposed such thatthe lateral surface of the end portion 295 of the cover 290 closer tothe light receiving element 223 does not intersect with the imaginaryline 19 connecting the light receiving portion of the light receivingelement 223 and the peripheral portion of the opening 272 a of thelight-receiving-element sealing portion 272. Accordingly, it is evenless likely that stray light reflected by the end portion of the cover290 will impinge on the light-receiving-element sealing portion 272. Itis thus possible to more effectively reduce the amount of stray lightwhich does not pass through a body and which is received through thecover 290.

In the biosensor 200, the end portion 294 of the cover 290 closer to thelight emitting elements 221 and 222 is disposed such that it does notoverlap the light-emitting-element sealing portion 271 when viewed fromthe direction normal to the principal surface 260 a of the wiring board260. Accordingly, it is less likely that light emitted from the lightemitting elements 221 and 222 will impinge on the end portion of thecover 290 through the light-emitting-element sealing portion 271. It isthus possible to further reduce the amount of stray light which does notpass through a body and which is transmitted through the cover 290.

In particular, in the biosensor 200, the cover 290 is disposed such thatthe lateral surface (end surface) of the end portion 294 of the cover290 closer to the light emitting elements 221 and 222 does not intersectwith the imaginary line 18 connecting the light emitting portion of eachof the light emitting elements 221 and 222 and the peripheral portion ofthe opening 271 a of the light-emitting-element sealing portion 271.Accordingly, it is even less likely that light emitted from the lightemitting elements 221 and 222 will impinge on the end portion 294 of thecover 290 through the light-emitting-element sealing portion 271. It isthus possible to more effectively reduce the amount of stray light whichdoes not pass through a body and which is transmitted through the cover290.

Modified Example

In the second embodiment, the rectangular sheet-like cover 290 is used.Alternatively, as shown in FIG. 6, a cover 390 having a hat-like shapein cross section so as to cover a sealing section 370 may be used.

As in the above-described biosensor 200, in this modified example, thecover 390 is disposed such that the lateral surface (end surface) of anend portion 394 of the cover 390 closer to light emitting elements 321and 322 does not intersect with the imaginary line 18 connecting thelight emitting portion (or the light emitting surface) of each of thelight emitting elements 321 and 322 and the peripheral portion of anopening 371 a of a light-emitting-element sealing portion 371. The cover390 is also disposed such that the lateral surface (end surface) of anend portion 395 of the cover 390 closer to a light receiving element 323does not intersect with the imaginary line 19 connecting the lightreceiving portion (or the light receiving surface) of the lightreceiving element 323 and the peripheral portion of an opening 372 a ofa light-receiving-element sealing portion 372.

In this mode, advantages comparable to those achieved by theabove-described biosensor 200 can be obtained. In this case, the cover390 does not have to have a flange. That is, the cover 390 may be formedin the shape of an inverted U shape in cross section having an openingfacing downward.

The embodiments of the present invention have been discussed. However,the present invention is not restricted to the above-describedembodiments, and various modifications may be made. For example, in thefirst embodiment, the end portions 154 and 184 of the base medium 151and the adhesion layer 180, respectively, are disposed farther inwardthan the opening 171 a so that they may not overlap the opening 171 a,and the end portions 155 and 185 of the base medium 151 and the adhesionlayer 180, respectively, are disposed farther inward than the opening172 a so that they may not overlap the opening 172 a. Alternatively, alight shielding portion may be formed around the light-emitting-elementsealing portion 171 and around the light-receiving-element sealingportion 172 (see the above-described second embodiment), and the endportions 154 and 155 of the base medium 151 and the end portions 184 and185 of the adhesion layer 180 may be disposed on the light shieldingportion formed as described above.

In the first embodiment, the adhesion layer 180 without a core member isused. Alternatively, double-sided tape including a core member made frompolyimide or PET and adhesive layers formed on both sides of the coremember may be used.

Moreover, in the above-described embodiments, two light emittingelements are provided. However, the number of light emitting elements isnot restricted to two, and one light emitting element may be provided,or three or more light emitting elements may be provided.

REFERENCE SIGNS LIST

-   -   100, 200, 300 biosensor    -   110, 210, 310 sensor unit    -   121, 122, 221, 222, 321, 322 light receiving element    -   123, 223, 323 light emitting element    -   130 first electrocardiograph electrode    -   140 second electrocardiograph electrode    -   150 base medium    -   160, 260, 360 wiring board    -   170, 270, 370 sealing section    -   171, 271, 371 light-emitting-element sealing portion    -   172, 272, 372 light-receiving-element sealing portion    -   173, 273, 373 light shielding portion    -   180 adhesion layer    -   290, 390 cover    -   10 normal direction    -   18, 19 imaginary line

1. A biosensor comprising: a wiring board; a light emitting element anda light receiving element disposed on a principal surface of the wiringboard; a light-emitting-element sealer disposed on the principal surfaceof the wiring board and adjacent to the light emitting element to sealthe light emitting element; a light-receiving-element sealer disposed onthe principal surface of the wiring board and adjacent to the lightreceiving element to seal the light receiving element; a light shieldingportion disposed between the light-emitting-element sealer and thelight-receiving-element sealer; a base medium with light transmittingproperties, disposed in parallel with the wiring board with the lightshielding portion therebetween; and an adhesion layer with lighttransmitting properties disposed between the base medium and at leastone of the light shielding portion, light-emitting-element sealer andthe light-receiving-element sealer, and the adhesion layer provided tobond the base medium with the at least one of the light shieldingportion, the light-emitting-element sealer portion and thelight-receiving-element sealer, wherein the adhesion layer and the basemedium do not overlap at least one of the light-receiving-element sealerand the light-emitting-element sealer when viewed from a directionnormal to the principal surface of the wiring board.
 2. The biosensoraccording to claim 1, further comprising a plane electrode disposed on aprincipal surface of the base medium such that the plane electrode doesnot overlap the light emitting element and the light receiving elementwhen viewed from the direction normal to the principal surface of thewiring board.
 3. The biosensor according to claim 2, wherein the planeelectrode is configured to monitor a potential of a body.
 4. Thebiosensor according to claim 2, wherein the plane electrode is disposedon the principal surface of the base medium such that the planeelectrode is between the light emitting element and the light receivingelement when viewed from the direction normal to the principal surfaceof the wiring board.
 5. The biosensor according to claim 1, wherein theadhesion layer and the base medium do not overlap both thelight-emitting-element sealer and the light-receiving-element sealerwhen viewed from the direction normal to the principal surface of thewiring board.
 6. The biosensor according to claim 1, wherein the lightemitting element comprises a pair of light emitting devices configuredto emit light beams at different wavelengths.
 7. The biosensor accordingto claim 6, wherein the pair of light emitting devices emit light in aninfrared light range and a red light range, respectively.
 8. Thebiosensor according to claim 1, wherein the light shielding portioncomprises a rectangular parallelepiped shape on the principal surface ofthe wiring board.
 9. The biosensor according to claim 1, wherein a firstend portion of the adhesion layer coincides with a lateral surface ofthe light-emitting-element sealer, and wherein a second end portion ofthe adhesion layer coincides with a lateral surface of thelight-receiving-element sealer.
 10. The biosensor according to claim 1,wherein a first end portion of the adhesion layer coincides with alateral surface of the light-emitting-element sealer, and wherein asecond end portion of the adhesion layer overlaps the light receivingelement when viewed from the direction normal to the principal surfaceof the wiring board.
 11. The biosensor according to claim 10, whereinthe second end portion of the adhesion layer overlaps a centerline ofthe light receiving element when viewed from the direction normal to theprincipal surface of the wiring board.
 12. The biosensor according toclaim 1, wherein a distance from the light emitting element to the lightreceiving element is between 4 mm and 20 mm.
 13. A biosensor comprising:a wiring board; a light emitting element and a light receiving elementdisposed on a principal surface of the wiring board; alight-emitting-element sealer disposed on the principal surface of thewiring board and adjacent to the light emitting element to seal thelight emitting element; a light-receiving-element sealer disposed on theprincipal surface of the wiring board and adjacent to the lightreceiving element to seal the light receiving element; a light shieldingportion disposed between the light-emitting-element sealer and thelight-receiving-element sealer; and a cover with light transmittingproperties, disposed in parallel with the wiring board with the lightshielding portion therebetween, wherein the cover is disposed such thecover does not overlap at least one of the light-receiving-elementsealer and the light-emitting-element sealer when viewed from adirection normal to the principal surface of the wiring board.
 14. Thebiosensor according to claim 13, wherein the cover does not overlap boththe light-emitting-element sealer and the light-receiving-element sealerwhen viewed from the direction normal to the principal surface of thewiring board.
 15. The biosensor according to claim 13, wherein the covercomprises a first end portion adjacent to the light receiving elementand a second end portion adjacent to the light emitting element.
 16. Thebiosensor according to claim 15, wherein a lateral surface of the firstend portion of the cover does not intersect an imaginary line connectinga light receiving portion of the light receiving element and aperipheral portion of an opening of the light-receiving-element sealer.17. The biosensor according to claim 15, wherein a lateral surface ofthe second end portion of the cover does not intersect an imaginary lineconnecting a light emitting portion of the light emitting element and aperipheral portion of an opening of the light-emitting-element sealer.18. The biosensor according to claim 13, wherein the light emittingelement comprises a pair of light emitting devices configured to emitlight beams at different wavelengths.
 19. The biosensor according toclaim 18, wherein the pair of light emitting devices emit light in aninfrared light range and a red light range, respectively.
 20. Thebiosensor according to claim 13, wherein the cover comprises an invertedU shape cross section having an opening facing downward.